Ultra-low reverse leakage NiOx/β-Ga2O3 heterojunction diode achieving breakdown voltage >3 kV with plasma etch field-termination

This work reports the fabrication and characterization of a NiOx/β-Ga2O3 heterojunction diode (HJD) that uses a metallic nickel (Ni) target to deposit NiOx layers via reactive RF magnetron sputtering and lift-off processing with >3 kV breakdown voltage, ultra-low reverse current leakage under high reverse bias, and a high junction electric field (>3.34 MV/cm). The heterojunction diodes are fabricated via bilayer NiOx sputtering followed by self-aligned plasma-etching for field-termination on both large (1-mm2) and small area (300/100-μm diameter) devices. The HJD exhibits an ∼135 A/cm2 forward current density at 5 V with a rectifying ratio of ∼1010. The minimum differential specific on-resistance was measured to be 17.26/11.64 mΩ cm2 (with/without current spreading). The breakdown voltage on a 100-μm diameter pad was measured to be greater than 3 kV with a noise floor-level reverse leakage current density (10−8 ∼ 10−6 A/cm2) up to 3 kV, accomplishing a parallel-plane junction electric field to be at least 3.34 MV/cm at 3 kV with a power figure of merit >0.52/>0.78 GW/cm2 (with/without current spreading). The temperature-dependent forward current density–voltage (J–V) measurements were performed from room temperature (25 °C) to 200 °C, which showed a temperature coefficient of resistance (α) of 1.56, lower than the value of SiC Schottky barrier diodes.